The meaning and origin of the expression: Fellow
traveller

Fellow traveller

What's the meaning of the phrase 'Fellow traveller'?

Someone
sympathetic toward a certain point of view without being a fully paid-up member
of the club.

What's the origin of the phrase 'Fellow traveller'?

In its literal meaning 'fellow traveller' just means someone who travels with you. It was first
applied to non-communists who were inclined toward the views of the Communist
Party by Leon Trotsky. He used the Russian word popútchik to indicate that. The term 'fellow traveller' in this sense came rather later, in the New York publication Nation, 1936:

"The new phenomenon is the fellow-traveler. The term has a Russian background and means someone who does not accept all your aims but has enough in common with you to accompany you in a comradely fashion part of the way. In this campaign both Mr. Landon and Mr. Roosevelt have acquired fellow-travelers."